--- gforth/unix/socket.fs	2011/04/13 20:11:12	1.43
+++ gforth/unix/socket.fs	2011/12/12 19:45:40	1.44
@@ -143,7 +143,10 @@ $802 Constant O_NONBLOCK|O_RDWR
 [THEN]
    1 Constant SOCK_STREAM
    2 Constant SOCK_DGRAM
+   0 Constant IPPROTO_IP
   41 Constant IPPROTO_IPV6
+  10 Constant IP_MTU_DISCOVER
+  23 Constant IPV6_MTU_DISCOVER
    4 Constant F_SETFL
 $001 Constant POLLIN
 $002 Constant POLLPRI
@@ -162,11 +165,13 @@ $004 Constant POLLOUT
 
 : new-udp-socket ( -- socket )
     PF_INET SOCK_DGRAM 0 socket
-    dup 0<= abort" no free socket" ;
+    dup 0<= abort" no free socket"
+    dup IPPROTO_IP IP_MTU_DISCOVER sockopt-on 1 over l! 4 setsockopt drop ;
 
 : new-udp-socket6 ( -- socket )
     PF_INET6 SOCK_DGRAM 0 socket
     dup 0<= abort" no free socket"
+    dup IPPROTO_IPV6 IPV6_MTU_DISCOVER sockopt-on 1 over l! 4 setsockopt drop
     dup IPPROTO_IPV6 IPV6_V6ONLY sockopt-on dup on 4 setsockopt drop ;
 
 \ getaddrinfo based open-socket